1. Field of the Invention
The invention relates to a sensing circuit. Particularly, the invention relates to a current sensing circuit.
2. Description of Related Art
A current sensing technique is widely applied for power management or sensor reading. Taking the sensor reading as an example, optical sensors are widely applied in mobile phones, handheld devices and image displays. Most of the optical sensors apply a photodiode structure. The optical sensor may generate different currents according to different intensities of sensed light.
Generally, to facilitate a signal process, a current value read by the sensor is generally converted into a digital signal. In a conventional technique, a commonly used signal processing method is to first convert a current into a voltage, and then a voltage-type analog-to-digital converter (ADC) is used to convert the voltage into a digital signal for the signal process. However, according to the foregoing digital signal converting method, besides that a circuit complexity cannot be reduced, an offset effect or a nonlinearity effect of the digital signal is occurred, and in applications of slow current variation, a high bit resolution cannot be achieved.